Mapping eucalypt forest susceptible to dieback associated with bell miners (Manorina melanophys) using laser scanning, SPOT 5 and ancillary topographical data

Mapping the location and extent of forest at risk from damaging agents or processes assists forest managers in prioritizing their planning and operational mitigation activities. In Australia, Bell Miner Associated Dieback (BMAD) refers to a form of canopy decline observed in eucalypt crowns occupied by colonies of bell miners (Manorina melanophrys). High densities of bell miners are associated with decreased avian abundance and diversity and an increase in psyllid abundance on crown foliage. BMAD has recently been nominated as a key threatening process in New South Wales (NSW). Consequently, a modelling system for predicting bell miner distribution in coastal eucalypt forests of NSW has been developed. The presence or absence of bell miners was recorded in 130 plots located within a 12,800 ha catchment study area containing a range of eucalypt forest types. The modelling system was produced by integrating a machine learning software suite (WEKA), and the statistical software R within the geographic resources analysis support system (GRASS) geographical information system (GIS). The variable modelled was the binary variable: presence or absence of bell minors. Six modelling techniques (Logistic regression; generalised additive models; two tree-based ensemble classification algorithms, random forest and Adaboost and Neural Networks) were integrated with airborne laser scanning; SPOT 5 and topographic derived variables. Model evaluation and parameter selection were measured by three threshold dependent measures (sensitivity, specificity and kappa) and the threshold independent Receiver Operator Curve (ROC) analysis. The final presence and absence maps were obtained through maximisation of the kappa statistic and applied at a resolution of 10 m across the entire catchment study area. For this data set, the most accurate algorithm for predicting the distribution of bell miner colonies was random forest (kappa = 0.84; ROC area under curve = 0.97). Variables most commonly selected in the six models were the laser scanning metrics; coefficient of variation, skewness, and the 10th and 90th percentiles derived from the shape of the height frequency distribution which, in turn, is directly influenced by vertical structure of the forest. An image textural statistic based on the shortwave infrared (SWIR) band of SPOT 5 was also commonly selected by the models. The SWIR band is sensitive to vegetation and soil moisture content. These models predicted that forest stands with a sparse eucalypt canopy over a moist, dense understorey were susceptible to being colonised by bell miners and hence BMAD.     

基于多普勒天气雷达数据的台风灾害评估系统

台风是影响我国的主要气象灾害之一,多普勒天气雷达是研究灾害性天气形成机理、结构特征的最重要手段。为进一步提高台风灾害评估的准确性和及时性,基于先进的多普勒天气雷达探测技术及时获取台风过程中的降水量、降水强度、最大风速作为动态因子,选取相对高度、坡度、经济易损性作为静态因子,利用可拓理论建立台风灾害评估模型,以ARCGIS作为开发平台,开发了台风灾害评估系统,实现了台风灾害评估的可视化和实时评估,为台风防灾减灾提供及时的决策服务。     

多波段激光防护塑料的研制

本文以PMMA为基质制备了多波段激光防护塑料样品,对其性能进行了测试,该样品对YAG激光有很好的防护作用,达到实用要求。     

毫米波云雷达与激光云高仪气象探测性能对比分析

为评估毫米波云雷达及激光云高仪的探测性能,选取广州市气象局KA波段毫米波云雷达和激光云高仪云高观测数据,通过对比两种测云设备在相同条件下的差异,分析不同要素对观测设备的影响,结果表明：(1)毫米波云雷达与激光云高仪同时探测到有云时,二者在云底高度观测上吻合程度较高,相关系数为0.98;(2)在数据获取率上,云雷达对高云的探测能力明显优于激光云高仪,但在对低云的探测能力上还有待提高,和激光云高仪相比,云雷达对低云和中云的识别能力有待提高;(3)对于多层云的观测,低层云的遮挡降低了激光云高仪对中高层云的观测,激光云高仪探测的中高层云多数在云雷达的回波内部.(4)对于不同强度的降水,日降水量越多,该天所测得的高、中云层回波就越少.(5)通过边界层高度与污染物的关系分析可以得出,边界层高度与PM2.5浓度呈反比.这些研究能够对毫米波云雷达和激光云高仪的探测能力进行评估,为后续选择设备提供参考,也推动了云观测技术的发展.     

基于Sentinel-1A极化SAR数据与面向对象方法的山区地表覆被分类

地表覆被分类对国土资源调查评估及全球变化具有基础性和关键性意义,但山区由于地形和云雾等的影响,可利用光学遥感影像和其他资源十分稀缺。因此,论文以渝东南山区为研究区,基于Sentinel-1A极化合成孔径雷达（SAR）数据,通过系列预处理,得到后向散射系数值,同时对各类地物的VV/VH极化后向散射系数、纹理、高程和坡度等特征值统计分析,综合这些特征值运用面向对象分类方法对单时相与多时相SAR数据进行地表覆被分类,最后将这两种分类方法与Landsat 8 OLI数据分类作对比。研究表明：1）在同时运用面向对象分类方法的前提下,单时相SAR数据分类和Landsat 8 OLI数据分类精度相当,多时相SAR数据面向对象分类精度最高,总精度为85.65%,Kappa系数为0.829 9;2）与光学数据相比,SAR数据对阔叶林、人工建筑提取有优势,精度提高了10%以上,多时相特征有利于耕地和针阔混交林提取,分类精度比单时相提高了9%左右;3）研究区土地覆被类型以林地为主,占总面积的42.68%,耕地、草灌次之,人工建筑、草地与河流占地面积较少。     

尾矿库初期坝稳定性的合成孔径雷达干涉变形检测与流固耦合数值模拟分析

某尾矿库初期坝采用分段施工,可能产生不均匀沉降,影响坝体的稳定性。采用孔径雷达干涉技术对尾矿库初期坝进行了短期变形速率观测,得出坝体右侧的后期填筑区域整体上与主体仍能够基本保持同步沉降。建立了三维流固耦合模型,分析了尾矿库初期坝的静力稳定性和渗流稳定性,结果表明:初期坝体的水平位移和竖向位移都在安全范围之内,考虑水和尾砂的共同作用,后期堆积坝堆积至1765m高程时,坝体顶部和后期回填区域,存在小量位移变形,静态稳定性安全系数达到2.25,初期坝能够保持稳定。     

雷达吸波涂层海洋大气环境适用性试验研究

目的分析一种雷达吸波隐身涂层在海洋大气自然环境下性能的变化规律。方法对12个月不同阶段涂层的常规物理性能和电性能进行检测,其中常规物理性能包括宏观形貌、金相形貌、微观性能、附着力、抗冲击强度和红外光谱。结果从宏观形貌看,涂层明度和色差值呈上升趋势,12个月明度增加1.22,色差值增加2.91,颜色向绿色和蓝色发展,失光率先增大、后减小,最大失光率为9个月时的34%。涂层附着力和试验时间呈现非线性关系,6个月时,附着力降低了18%,12个月时增大了24%。涂层在2~18GHz的频率范围内,吸波曲线大体呈“U”形,最低反射率随时间向低频方向偏移。涂层金相形貌、微观性能、抗冲击强度和红外光谱特征总体变化不明显。结论在1a内,自然海洋大气环境对雷达吸波隐身涂层常规物理性能和电性能产生了一定影响,但在试验时间相对较短情况下,海洋大气环境对涂层老化的影响作用尚未充分显示,需要结合更长周期的试验数据进一步分析。